What Does P1550 Mean?
The idle speed control valve closing solenoid has an electrical circuit fault. The PCM cannot properly control idle speed, which may result in rough idle, stalling, or high idle conditions.
Common Causes
40%
Failed idle air control valve or solenoid
25%
Wiring harness damage or connector corrosion
20%
Carbon buildup restricting IAC valve movement
10%
Open or shorted circuit in IAC wiring
5%
PCM internal driver circuit failure
Diagnostic Steps
1
Step 1: Inspect IAC valve connector for corrosion or damage
2
Step 2: Measure IAC valve solenoid resistance (typically 10-14 ohms per winding)
3
Step 3: Remove and clean IAC valve and throttle body passages
4
Step 4: Test IAC valve operation with scan tool commanded position changes
5
Step 5: Check wiring continuity and voltage supply from PCM to IAC valve
Estimated Repair Cost
$100 - $450
Parts + labor, varies by vehicle and location
The idle speed control valve closing solenoid has an electrical circuit fault. The PCM cannot properly control idle speed, which may result in rough idle, stalling, or high idle conditions.
The most common cause of P1550 (Idle Speed Control valve Closing Solenoid Control Circuit Electrical) is: Failed idle air control valve or solenoid
Typical repair costs for P1550 range from $100 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle may stall at idle or intersections, creating potential safety hazard. Repair recommended soon.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1550 to identify the root cause.
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Quick Info
Category
Powertrain
System
Idle Air Control
Difficulty
Type
Manufacturer
Recommended Tools
OBD2 Scanner
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